arXiv subjects

Karl D. Briegel

Publications and source records attributed to Karl D. Briegel.

5 recordsLinked to original sources

arXiv2026

Coherent signal detection in the statistical polarization regime enables high-resolution nanoscale NMR spectroscopy

Nitrogen-vacancy (NV) centers in diamond have emerged as quantum sensors capable of detecting nuclear magnetic resonance (NMR) signals at unprecedented length scales, ranging from picoliter sample volumes down to single spins at the diamond surface. While high-resolution (few-hertz) coherent NV-NMR spectroscopy has been demonstrated at the micrometer scale, achieving comparable resolution at the nanometer scale has remained elusive. In this nanoscale regime, sensing relies on detecting stochastic spin noise from statistical polarization, where molecular diffusion in liquid samples severely broadens the spectrum and degrades resolution. Here, we demonstrate that coherent detection of signals from a hyperpolarized nanoscale sample overcomes this limitation, enabling single-digit hertz spectral resolution and the capacity to resolve scalar couplings. Finally, building on these results, we present a comparative analysis of the sensitivity of coherent versus spin-noise detection, identifying the regimes in which each performs best.

physics.chem-ph↗

arXiv2026

Development of a Modular Optically Detected Magnetic Resonance Setup for Optical Experiments in a Variable Temperature Insert

We developed an optically detected magnetic resonance (ODMR) setup designed for compatibility with a widely used, commercially available helium bath cryostat equipped with a variable temperature insert. The optical path extends nearly two meters, spanning the full length of the cryostat insert, enabling excitation of the nitrogen-vacancy (NV) centers and detection of the resulting fluorescence from outside the cryostat. The setup preserves optical alignment and beam quality along this extended path allowing integration into existing cryogenic systems without significant modifications. We demonstrate the setup's performance by measuring the temperature dependence of the resonance signal and its behavior under small applied magnetic fields, as well as the magnetic transition of a SrRuO$_3$ sample, thereby showcasing the feasibility of NV magnetometry on a sample in constrained cryogenic environments.

physics.ins-det↗

arXiv2024

Time-space encoded readout for noise suppression and scalable scanning in optically active solid-state spin systems

Optically active solid-state spin systems play an important role in quantum technologies. We introduce a new readout scheme, termed Time to Space (T2S) encoding which decouples spin manipulation from optical readout both temporally and spatially. This is achieved by controlling the spin state within a region of interest, followed by rapid scanning of the optical readout position using an acousto-optic modulator. Time tracking allows the optical readout position to be encoded as a function of time. Using nitrogen-vacancy (NV) center ensembles in diamond, we first demonstrate that the T2S scheme enables correlated experiments for efficient common mode noise cancellation in various nano- and microscale sensing scenarios. In the second example, we show highly scalable multi-pixel imaging that does not require a camera and has the potential to accelerate data acquisition by several hundred times compared to conventional scanning methods. We anticipate widespread adoption of this technique, as it requires no additional components beyond those commonly used in optically addressable spin systems.

physics.app-ph↗

arXiv2024

Optical Widefield Nuclear Magnetic Resonance Microscopy

Microscopy enables detailed visualization and understanding of minute structures or processes. While cameras have significantly advanced optical, infrared, and electron microscopy, imaging nuclear magnetic resonance (NMR) signals on a camera has remained elusive. Here, we employ nitrogen-vacancy (NV) centers in diamond as a quantum sensor, which converts NMR signals into optical signals that are subsequently captured by a high-speed camera. Unlike traditional magnetic resonance imaging (MRI), our method records the NMR signal over a wide field of view in real space. We demonstrate that our optical widefield NMR microscopy (OMRM) can image NMR signals in microfluidic structures with a $\sim 10\,μm$ resolution across a $\sim 235 \times 150\,μm^2$ area. Crucially, each camera pixel records an NMR spectrum providing multicomponent information about the signal's amplitude, phase, local magnetic field strengths, and gradients. The fusion of optical microscopy and NMR techniques enables multifaceted imaging applications in the physical and life sciences.

physics.app-ph↗

arXiv2022

Advances in nano- and microscale NMR spectroscopy using diamond quantum sensors

Quantum technologies have seen a rapid developmental surge over the last couple of years. Though often overshadowed by quantum computation, quantum sensors show tremendous potential for widespread applications in chemistry and biology. One system stands out in particular: the nitrogen-vacancy (NV) center in diamond, an atomic-sized sensor allowing the detection of nuclear magnetic resonance (NMR) signals at unprecedented length scales down to a single proton. In this article, we review the fundamentals of NV center-based quantum sensing and its distinct impact on nano- to microscale NMR spectroscopy. Furthermore, we highlight and discuss possible future applications of this novel technology ranging from energy research, material science, or single-cell biology, but also associated challenges of these rapidly developing NMR sensors.

quant-ph↗